Abstract
Purpose :
Eye diseases or external stress such as excessive light exposure can cause global changes in the function and structure of various retinal neurons and glia. Quantitative determination of the complex pathophysiological events in intact retinal networks is challenging. Here I develop a novel method to study the functional state of distinct cell types in healthy and diseased retina affected by autosomal dominant P23H mutation by using Ex Vivo Electroretinography.
Methods :
Ex vivo ERG responses to flashes of light were recorded from intact WT and RhoWT/P23H (P23H) mouse retina explants. ON bipolar cell (Rb) and Müller cell (Rc) components were isolated by subtracting light responses recorded after blocking these components by DL-AP4 and Barium , respectively, from those recorded before application of the blockers. Photoreceptor responses (a wave) were isolated in the presence of both DL-AP4 and Barium. The functional state of the rods, bipolar cells and Müller cells were analyzed by plotting the respective components as a function of flash intensity, rod response amplitude (Rp) and the area under the pharmacologically isolated a-waves (A), respectively.
Results :
The maximal Rp was 400 μV in control mice and decreased to 250 μV in 1 mo and to 140 μV in 3 mo P23H mice while the flash intensity producing half-maximal response did not change in P23H mutants. Surprisingly, bipolar cell response did not decline in 1 mo P23H mice. Moreover, the photoreceptor input needed for the half-maximal bipolar cell response (Rp,1/2) was actually decreased >2-fold in 1 mo P23H mice showing the increased sensitivity of rod – bipolar cell signaling at the onset of rod degeneration. At 3 mo P23H mice bipolar cell response declined but the Rp,1/2 remained significantly smaller as compared to WT mice. Müller cell responses behaved linearly as a function of A with a steeper slope up to the range where photoreceptors started to saturate and shallower slope beyond that.
Conclusions :
A new method was used to reveal a potentiation of rod-bipolar cell signaling in response to slow rod photoreceptor degeneration in the P23H mice. In the future I will use this method to determine the functional state of rod/cone-bipolar cell signaling and Müller cells in various models of retinal disease including retinitis pigmentosa and diabetic retinopathy.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.